We have identified a 17 kilodalton collagenous component which is synthesized by bone marrow cells in culture and by organ cultures of demineralized bone matrix implanted intramuscularly. Temporal changes in the synthesis of this 17k collagen showed that synthesis is elevated at 7 days and represents approximately 12 percent of the total collagen, decreasing to 6 percent by 28 days. Experiments in cell cultures have given similar results, showing an initially high followed by a decrease in 17k synthesis. A polypeptide component with the same molecular weight and collagenous properties was identified from cell free translation of mRNA prepared from chondrocytes. Bone marrow cells produce large quantities of 17k by comparison with other cells. We plan to purify this protein from bone marrow cell cultures using a combination of salting out, ion exchange, gel filtration and affinity chromatography procedures. The purified protein will be used for the preparation and characterization of monoclonal antibodies and for the determination of partial amino acid sequences on both the intact protein and on major fragments obtained by chemical and enzymatic cleavage. Our objectives are to prepare synthetic oligonucleotides corresponding to appropriate amino acid sequences obtained from the protein. Since synthesis of 17k decreases with time, factors that regulate its production may be important to the formation of new mesenchyme. The effect of growth factors on extracellular matrix production by bone marrow cells in culture will be investigated. Changes in the synthesis of collagen types including 17k, will be determined and compared with levels of fibronectin and glycosaminoglycan synthesis. The effect of exogenous proteins on cell adhesion, cell morphology and protein synthesis will be studied. The effect of major extracellular matrix components such as collagen and fibronectin on 17k in bone marrow cell cultures will be examined. The long term objectives of this proposal are to determine the regulation that may be involved in the control of expression of this protein.